In general, drug delivery through the skin is achieved by electrophoresis or electroosmosis. The drug administered transdermally in this manner reaches the bloodstream, being aided by ions. In particular, in case of electroosmosis, aqueous solution is attracted to the negative (−) electrode and current flows via membrane with small pores.
Drug administration using devices related to these techniques is quite limited. U.S. Pat. Nos. 2,493,155, 4,141,359, 4,250,878, 3,163,166, 4,166,457, 4,273,135, 3,289,671, 4,239,052, 4,367,745, 3,677,268 and 4,243,052 disclose methods for administering drugs through skin.
Particularly, it is to be noted that, according to U.S. Pat. Nos. 3,289,671 and 4,141,359, the rate of drug administration is a function of current and the control of current is critical in controlling the amount of drug administration. U.S. Pat. No. 588,479 discloses an electric herb pad providing electrical effect as well as herbal medicinal effect at the same time for human body.
Iontophoresis is a transdermal drug administration technique capable of complementing or replacing existing oral administration or injection. Differently from the passive drug transport using a pad attached to the skin, it enables active transport of soluble drug through the skin using electric induction. In an iontophoretic apparatus, a drug pad containing drug is attached to the skin. Then magnetic or electrical stimulation is applied to the drug pad such that the drug pad is maintained in a positively or negatively charged state and the drug is penetrated into the skin owing to electrical or magnetic repulsion. The iontophoretic technique is used in cooling or heating pads for drug delivery.
Korean Patent No. 0775675 discloses a vibration pad to stimulate the body for physiotherapy and an apparatus for controlling the same.
The pad is configured such that the drug ingredient is easily absorbed into the skin by applying electric field or magnetic field to a medicinal ingredient layer formed in the pad.
However, the patent focuses only on the fast penetration of drug without considering the persistence of the drug administration through the skin and, thus, it is difficult to persistently administer the drug through the skin. Moreover, it is impossible to vary the rate of penetration depending on the particular drug included in the medicinal ingredient layer.
When preparing herbal medicine from plants by mixing different ingredients obtained from, for example, the whole plant, leaves, root and rhizome, fruit and seed, flower, bark, stem, or the like, it may be necessary to control the time or amount of penetration into the skin according to pharmacological effect so as to achieve persistent drug delivery, which is difficult to be achieved with existing pads or patches.